It is common in decorative light strings to have light units comprising miniatures bulbs each seated in a socket provided by a holder which has a push-in fit with a housing having a socket containing two contact elements extending into a wireway in the base of the housing. The contact elements engage wires of the light string extending through the wireway. Each bulb has a pair of fine single-strand wire leads extending from the bulb through the base of the holder and doubled back about one-half inch against the outside of the holder so as to be pressed into engagement with the contact elements when the holder is pushed into the holder socket. Assembly of the bulb in the holder and the mounting of the bulb and holder in the housing are performed manually and require deft manipulation of the lead wires. Consequently, the doubled back portion of each bulb lead does not always end up in a position generally parallel to the longitudinal axis of the respective holder when the bulb is pushed into the housing socket. As a result there may be in some instances no initial contact between the lead and the respective contact element or later loss of contact after assembly during handling of the respective light set.